A practical test of the link between perceived identifiability and prosociality with two field studies

Covering the face with masks in public settings has been recommended since the start of the pandemic. Because faces provide information about identity, and that face masks hide a portion of the face, it is plausible to expect individuals who wear a mask to consider themselves less identifiable. Prior research suggests that perceived identifiability is positively related to prosocial behavior, and with two pre-registered field studies (total N = 5706) we provide a currently relevant and practical test of this relation. Our findings indicate that mask wearers and non-wearers display equivalent levels of helping behavior (Studies 1 and 2), although mask wearers have a lower level of perceived identifiability than those without a mask (Study 2). Overall, our findings suggest that claims that face masks are related to selfish behavior are not warranted, and that there is no practical link between perceived identifiability and prosocial behavior.


Research assistants' gender
The overall mean for the prosocial measure did not significantly differ when comparing the data collected by male research assistants vs. the female ones. Mfemale = 18.63,SDfemale = 36.12,Mmale = 14.24,SDmale = 32.68,t(396) = 1.124,, d = 0.12, 95% CI [-0.09, 0.34] The conclusion of our hypothesis test remained unchanged when analyzing the data collected by male and female research assistants separately, although the direction of the effect is different. However, the conclusion of our hypothesis test remained unchanged when analyzing the data for male only or female only participants.

Floor and ceiling effects
When excluding all the participants who did not answer any of the questions and were coded at the level 0 for the prosocial measure, the result of the hypothesis test remained unchanged. Mmask = 69.5, SDmask = 35.51, Mno mask = 74.89, SDno mask = 33.61, t(94) = 0.76, p = 0.2239 (one-tailed), d = 0.16, 95% CI Infinity] When excluding all the participants who answered all of the questions and were coded at thelevel 102 for the prosocial measure, the result of our hypothesis test also remained unchanged. Hence, it is unlikely that the "floor" and "ceiling" effects influence our conclusions.

Mask status change
When including participants who changed their mask status during the interaction by coding them according to how they were when they were approached (i.e., participants who had a mask but removed it were included in the Mask group and participants who didn't have a mask but put one on were included in the No Mask group), the results of the hypothesis test remained unchanged. Mmask = 19.26, SDmask = 36.51, Mno mask = 17.2, SDno mask = 35.51, t(409) = -0.58, p = 0.7183 (one-tailed), d = -0.06, 95% CI Infinity] When including these participants by coding them according to how they were at the end of the interaction (i.e., participants who put a mask on were included in the Mask group and participants who removed their mask were included in the No Mask group), the results of the hypothesis test also remained unchanged. When comparing the two groups with a Mann-Whitney U-test, the difference remains non-significant U(Nmask = 186, Nno mask = 212) = 0.52322, z = 1.0714, p = 0.142 (one-tailed) The participants 3,9,22,28,34,35,36,61,64,65,71,72,73,127,146,148,151,152,158,162,171,181,188,192,208,226,236,238,249,257,272,278,280,281,293,294,296,298,304,305,307,308,316,340,341,347,351,386,401,403,407 and 414 have been identified as having a Cook's distance greater than three times the mean Cook's distance of the sample for a model predicting the prosocial measure score by the Mask variable.
However, the conclusion of our hypothesis test remains unchanged when excluding these participants.  Among the participants who answered at least the first two questions (i.e., age and occupation on the first page), participant age was not correlated to the prosocial measure t(655) = 1.7549, p = 0.0797, r = 0.068, 95% CI [-0.008, 0.14] Students Among the participants who answered at least the first two questions, the overall mean for the prosocial measure did not significantly differ when comparing those who were students (M = 62.98, SD = 39.76) and those who weren't students (M = 69.03, SD = 38.93 ; t(650) = 1.9307, p = 0.05395 (two-tailed), d = 0.15, 95% CI [0, 0.31]).
And the result of our hypothesis test remained unchanged when excluding students. t(5042) = -6.107, p < 0.001 (TOST) Psychology-related activity Among the participants who answered at least the first two questions, the overall mean for the prosocial measure did not significantly differ when comparing those who had an activity related to psychology (M = 72, SD = 32.74) and those who didn't have an activity related to psychology (M = 66.53, SD = 39.42 ; t(650) = -0.33846, p = 0.7351 (two-tailed), d = -0.14, 95% CI [-0.94, 0.67]).
And the result of our hypothesis test remained unchanged when excluding those who had an activity related to psychology. t(5300) = -5.525, p < 0.001 (TOST) Floor and ceiling effects When excluding all the participants who did not answer any of the questions and were coded at the level 0 for the prosocial measure, the result of the hypothesis test was non-significant. Hence, there is a possibility that the "floor effect" has impacted our results.
With a logistic regression with a two-level categorical outcome variable, there is no significant difference between the Mask and No Mask group.
The odds of agreeing to answer the survey for the No Mask group was 0.13, 95% CI [0.11, 0.14], and the estimated odds ratio favored an increase of 1.32, 95 % CI [1.12, 1.55] of agreeing to answer the survey for the Mask group.